I. Field of the Invention
The present invention relates to testing adhesion layers. More particularly, this invention describes methods and systems for testing the quality of tack coat layers applied on road surfaces before placement of an overlay to provide for bonding.
II. Description of Related Art
The U.S. Department of Transportation Federal Highway Administration estimates that about 50% of the interstate system and about 70% of all highways in the U.S. are paved with hot-mix asphalt concrete (HMAC). However, there is evidence that the number of premature distresses to the constructed asphalt pavement is increasing. Factors such as heavier truck axle weights, increased tire pressures, increased traffic loading, and/or inadequate drainage contribute to the deterioration of the pavement system.
Typically, to strengthen the deteriorated pavement system, an overlay of HMAC (approximately 2 in thick) is placed on top of the existing pavement. This tack coat, comprising materials such as emulsions or asphalt cements, is generally applied to existing surfaces prior to applying an overlay. The tack coat acts as a thin layer that bonds overlay to the existing surface. In cases where bond loss occurs between the existing surface and the overlay, a slippage occurs between the layers, causing failure. The loss of bondage can be attributed to at least the following: quality of the tack coat, application of the tack coat, dilution of the tack coat, and materials settling on the tack coat (e.g., dust, rainfall, etc.) prior to applying the overlay
As such, it is necessary to be able to test the strength of the tack coat prior to the application of the overlay. Current methods observe and analyze samples in laboratories to determine the best tack coat type and rate of application of the tack coat. However, laboratory observation does not factor in environmental constraints that may alter the composition and effectiveness of the tack coat. Further, laboratory evaluations do not allow for on-site evaluation of the tack coat to insure the quality of the tack coat prior to applying the overlay.
The referenced shortcomings are not intended to be exhaustive, but rather are among many that tend to impair the effectiveness of previously known techniques concerning testing of a tack coat; however, those mentioned here are sufficient to demonstrate that the methodologies appearing in the art have not been altogether satisfactory and that a significant need exists for the techniques described and claimed in this disclosure.